Wireless charging, also known as Wireless Power Transfer (WPT), is a technology that enables a power source to transmit electromagnetic energy to an electrical load across a gap, without interconnecting cords. Two directions for WPT are radiative wireless charging, which transfers energy via, for example, radiating electromagnetic, ultrasound, or acoustic waves and non-radiative charging, which transfers energy via an oscillating electromagnetic field.
The operation of the WPT requires both a Power Transmitting Unit (PTU) and a Power Receiving Unit (PRU) interface with each other through respective transmit and receive coils. The PTU includes a power generating unit that generates a DC voltage and converted to an AC voltage for driving the transmit coil. The transmit coil is typically configured as part of an H-bridge driver. Multiple different types of drivers can be utilized for realizing this H-bridge driver, such as Class D and Class E amplifiers.